The Amazon Linux AMI is based on RHEL 5.x and parts of RHEL6. One of our goals is binary compatibility with RHEL 5.x, and therefore CentOS5.x. Astute users will note that our kernel is based on 2.6.34, and we have engineered the image to conform to a cloud environment. For example, the lack of Xorg support helps to keep the images small and lean. The goal of the Amazon Linux AMI is to provide an image for use in the cloud and to serve as reference image of EC2 best practices. The maintenance (security, enhancements, features and bug fixes) for the image will come directly from Amazon, while maintaining maximum compatibility, security and functionality.

In computing, paravirtualization is a virtualization technique that presents a software interface to virtual machines that is similar but not identical to that of the underlying hardware.

The intent of the modified interface is to reduce the portion of the guest’s execution time spent performing operations which are substantially more difficult to run in a virtual environment compared to a non-virtualized environment. The paravirtualization provides specially defined ‘hooks’ to allow the guest(s) and host to request and acknowledge these tasks, which would otherwise be executed in the virtual domain (where execution performance is worse.) Hence, a successful paravirtualized platform may allow the virtual machine monitor (VMM) to be simpler (by relocating execution of critical tasks from the virtual domain to the host domain), and/or reduce the overall performance degradation of machine-execution inside the virtual-guest.

Paravirtualization requires the guest operating system to be explicitly ported for the para-API — a conventional O/S distribution which is not paravirtualization-aware cannot be run on top of a paravirtualized VMM. However, even in cases where the operating system cannot be modified, components may be available which confer many of the significant performance advantages of paravirtualization; for example, the XenWindowsGplPv project provides a kit of paravirtualization-aware device drivers, licensed under GPL, that are intended to be installed into a Microsoft Windows virtual-guest running on the Xen hypervisor.